The tests included the determination of the reinforcement effectiveness of old larch timber originating from a building built in 1860 with the use of carbon-fibre and aramid-fibre mats and strips, BFRPs and GFRPs. The test results showed that in old solid timber pieces from European larch (Larix decidua Mill.), the highest mean flexural bending capacity occurred in samples reinforced with carbon-fibre mats (increase in flexural bending capacity was 60.66% in relation to non-reinforced elements), while the lowest flexural bending capacity of the tested components occurred with reinforcement with GFRP (10 mm in diameter) (increase by only 19.04% in relation to non-reinforced elements). Additionally, bending tests of repaired 130-year-old pine (Pinus sylvestris L.) beams were shown (real-size scale) using CFRP strips and mats. The problems associated with the delamination of the CFRP strip due to uneven deformation of the damaged timber surface and the effectiveness of these repairs are also shown.
This article presents experimental results from the bending of technical-scale models of beams reinforced in the tension zone with CFRP (Carbon Fiber Reinforced Polymers) materials, with a focus on the benefits resulting from the increased ductility in the tension zone of these beams. In experimental tests, the mechanical properties of reinforced beams were compared with unreinforced beams in terms of the maximum load, deflection, images of damage, stiffness, and distribution of deformation. The results showed that the proposed reinforcement solution was advantageous due to its strength and stiffness, and the safety of the structure. Based on this analysis, it was concluded that the reinforcement of wood with CFRP materials has a positive effect on the behavior and safety of structures. Also, a method of analytical checking of strengthened beams with small cross-sections was presented in the article.
The purpose of this paper is to demonstrate the properties of glued laminated beams made in diverse configurations of timber quality classes, reinforced using a new technique that is cheaper and easy to apply. The aim of the experimental investigations was to enhance reinforcement effectiveness and rigidity of glued laminated beams. The tests consisted of four-point bending of large-scale specimens reinforced with basalt fibres (BFRP). The tests were meant to obtain images of failure, the load–displacement relation and load carrying capacity of basalt fibres depending on the reinforcement ratio. The tests, which concerned low and average quality timber beams, were conducted in a few stages. The aim of the study was to popularize and increase the use of low-quality timber harvested from reafforested areas for structural applications. In the study, theoretical and numerical analysis was carried out for reinforced and unreinforced elements in various configurations of wood quality classes. The aim was to compare the results with the findings of experimental tests. Based on the tests, it was found that the load carrying capacity of beams reinforced with basalt fibre was higher by, respectively, 13% and 20% than that of reference beams, while their rigidity improved by, respectively, 9.99% and 17.13%. The experimental tests confirmed that basalt fibres are an effective structural reinforcement of structural timber with reduced mechanical properties.
In recent years, we have seen the construction of numerous good-looking buildings, each of which is perfectly safe, resistant to weather conditions, durable and economically efficient. Apart from their use in the structures of new buildings, natural fibres are even more important in the field of restoring historical heritage. The article presents experimental testing of old wooden beams made of the European larch Larix decidua Mill. with natural defects (knots, natural grain, deviations, cracks and voids) on a technical scale, reinforced with natural fibre. The tests were carried out to examine the response of heterogeneous wooden beams during bending with reinforced basalt fibres (BFRP). The wooden beams were cut out from the ceiling of an old building from 1860. The tests of reinforced wooden beams were intended to determine the increase in bearing capacity and rigidity after providing natural reinforcement. The tests allowed for determining the deflection, the distribution of deformations and images of failure for non-reinforced and reinforced beams. The performed tests have shown the effectiveness of the application of basalt fibres (BFRP) to the improvement of structural properties of existing beams, thus allowing an increase in flexural strength. It can be concluded that reinforcements using BFRP materials can be applied both to strengthening the existing structures with deteriorated mechanical properties, as well as to reduce the dimensions of a structure. Experimental tests have proven that, in the case of beams reinforced with natural basalt (BFRP), their rigidity increases by ca. 15.17% compared to the reference beams.
The article presents results of an experimental studies on reinforcement of pine beams made from glued laminated timber with subsurface basalt fibers (BFRP). An experimental research program was presented, in which the bending strength of glued laminated timber of middle and lower quality class was increased after using BFRP basalt fabrics. Thanks to the use of BFRP reinforcement, an average load capacity increased by 47% and stiffness by 6% in comparison to non-reinforced elements. Based on the research, it was found that the use of BFRP basalt fabrics is an effective method for strengthening damaged wooden elements. Thus, it is an environmentally friendly method of improving the static work of structural elements by combining wood with other natural materials such as basalt fiber reinforced polymers.
Changes in the condition of existing timber structures can be caused by fatigue or biological attack, among other things. Replacing damaged timber is still very expensive, so it seems more advisable to repair or reinforce damaged elements. Therefore, in order to improve the static performance analysis of timber structures, reinforcement applications in timber elements are necessary. In this experimental study, technical-scale glulam beams measuring 82 × 162 × 3650 mm, which were reinforced with carbon strands and carbon laminates, were tested in flexure. A four-point bending test was used to determine the effectiveness of the reinforcement used in the timber beams. Internal strengthening (namely, glued carbon cords placed into cut grooves in the last and penultimate lamella) and an external surface of near-surface mounted (NSM) carbon laminates glued to the bottom surface of the beam were used to reinforce the laminated ashlar beams. As a result of this study, it was found that the bending-based mechanical properties of ash wood beams reinforced with carbon fibre-reinforced polymer composites were better than those of the reference beams. In this work, the beams were analysed in terms of the reinforcement variables used and the results were compared with those for the beams tested without reinforcement. This work proves the good behaviour of carbon fibre reinforced plastic (CFRP—Carbon fibre reinforced polymer) cords when applied to timber beams and carbon laminates. This study illustrated the different reinforcement mechanisms and showed their structural properties. Compared to the reference samples, it was found that reinforcement with carbon strings or carbon laminates increased the load-bearing capacity, flexural strength and modulus of elasticity, and reduced the amount of displacement of the timber materials, which is an excellent alternative to the use of ashlar and, above all, inferior grade materials due to the current shortage of choice grade. Experimental results showed that, with the use of carbon fibre (carbon cords SikaWrap® FX-50 C—Sika Poland Sp. z o.o., Warsaw), the load bearing capacity increased by 35.58%, or with carbon cords SikaWrap® FX-50 C and carbon laminates S&P C-Laminate type HM 50/1.4 - S&P Poland Sp. z o.o., Malbork, by 45.42%, compared to the unreinforced beams.
Reinforced concrete (RC) structures are basically composite elements because they consist of two materials—concrete and reinforcement (reinforcing steel bars). From the point of view of the design of new constructions, it is necessary to design them in such a way as to ensure their reliability, safety and durability throughout their design lifetime, Td. However, all elements, including RC members, are affected by the environment in which they are located. An aggressive environment causes degradation of materials. In the case of reinforcement, corrosion of the reinforcement is considered to be the most well-known and at the same time the most serious way of degradation. From the point of view of existing reinforced concrete elements, it is therefore important to know whether and how the corrosion of the reinforcement affects the mechanical properties of the given reinforcement. The mechanical properties of reinforcement are very important when assessing the actual condition of reinforced concrete (RC) elements, to determine the resistance and load-carrying capacity of the elements. Therefore, it is necessary to investigate the effect of corrosion on mechanical properties of reinforcement. The paper reports on the results of an experimental analysis of the effect of corrosion on the change in the mechanical properties of reinforcement. Furthermore, it presents both the redistribution of mechanical properties along the cross-section of reinforcement, produced by various techniques, such as hot-rolling, hot-rolling with controlled cooling from rerolling temperature and cold-rolled as well as the mechanical properties under the action of corrosion.
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